Thermally stimulated current and electro-optic responses in a main- and side-chain photorefractive polymer

The polarization and depolarization behavior of electric field-induced polar alignment in a side- and main-chain photorefractive polymer was measured by thermally stimulated current (TSC) and electro-optic (EO) modulation experiments. A relaxation peak was observed around the glass transition temperature (T_g) for the poled photorefractive polymer in a TSC experiment. The apparent TSC was not observed at room temperature. The polarization calculated from the relaxation peak linearly increased with the strength of the poling electric field. This result was consistent with the EO behavior which showed the linear dependence of the EO coefficients on the poling electric field. The main- and side-chain photorefractive polymer could be aligned by the electric field at an elevated temperature, and the polar alignment was stable at room temperature, which could lead to the long-term stability of the photorefractive responses without an external applied electric field.